Displays, in particular, displays mounted on mobile terminals are required to reduce power consumption. As means for reducing the power consumption of a drive circuit which drives liquid crystal, lowering a frequency for the circuit to update a video signal from a standard frequency of 60 Hz has been proposed (for example, JP 2002-278523 A). Since the circuit power consumption is proportional to the frequency, an effect of reducing the power consumption can be obtained.
However, if the frequency is lowered, a problem that flicker becomes conspicuous appears. If a time to recharge the video signal becomes long, a voltage of the liquid crystal cannot be held and the luminance of the liquid crystal is degraded due to an off-leak current of a thin-film transistor (TFT) of the drive circuit. This luminance degradation periodically occurs and results in flicker. To suppress occurrence of the flicker, the voltage of the liquid crystal needs to be held. The present invention therefore relates to a technology for suppressing voltage variation in the liquid crystal.